Helical multiple pump



Aug. 31, 1965 s. s. L. CHANG HELICAL MULTIPLE PUMP Filed Nov. 5, 1962INVENTOR. SHELDON S.L.CHANG,

by M

United States Patent 3,203,350 HELICAL MULTIPLE PUMP Sheldon S. L.Chang, Bronx, N.Y., assignor to Robbins & Myers, 1nc., Springfield,Ohio, a corporation of Ohio Filed Nov. 5, 1962, Ser. No. 235,182 6Claims. (Cl. 103-4) This invention relates to a helical multiple pumpand more particularly to a multiple pump such as is disclosed in theMoineau Patent No. 2,483,370. The individual pumping elements of such apump are disclosed in the Moineau Patent No. 1,892,217.

According to the earlier of said patents, a pair of helically threadedmembers in engagement one with the other, the outer elements having onemore thread than the inner element, cooperate to produce a series ofpumping pockets which travel from end to end through the pump.Generally, the outer pumping element is fixed or stationary and theinner element is rotated. The configuration of the cooperating threadsenforce upon the axis of the rotor an orbital path in a circle.

The action of such a pump in pumping fluids produces an axial thrust onthe rotor and in order to neutralize this axial thrust, Moineau in hisPatent 2,483,370 proposed to provide two such sets of pumping elementsin axial alignment with the rotors of the two pumps being joinedtogether to provide a common rotor. The two sets of pumping elements, orgears as he called them, were provided with threads of opposite hand andpumping could be achieved, depending upon the rotation of the rotor fromthe outer ends of the two sets of pumping elements toward the middle andthence to an outlet or from an inlet at the middle of the pump outwardlythrough the two sets of pumping elements to a manifold leading to thepump outlet.

As Moineau pointed out in his Patent No. 2,483,370, careful orientationof the stator and rotor are necessary and particularly orientation ofone of the stators with respect to the common rotor. This requirementfor careful phasing or orientation has prevented a multiple pump asproposed by Moineau from becoming commercial.

It should be noted that while the rotor rotates, it is forced to nutateagainst hydraulic pressure by the stator element. The reaction force ofthe rotor against the stator causes a deformation of the stator and thealignment or phasing is different for different hydraulic pressures.Thus, even with perfect alignment when the pump is not under operation,the alignment will be imperfect once the desired pressure is built up.This effect is more severe when the stator is made of resilientmaterial, like rubber.

Accordingly, it is the principal object of the present invention toprovide a pump of the general type disclosed in the later of the twosaid Moineau patents, wherein the problem of phasing is solved in a verysimple and economical manner.

This and other objects of the invention which will be disclosed in moredetail hereinafter or which will become apparent to one skilled in theart upon reading these specifications are accomplished by that certainconstruction and arrangement of parts of which the following willdescribe two exemplary embodiments.

Reference is made to the drawings forming a part hereof and in which:

FIG. 1 is a cross-sectional view in more or less diagrammatic form ofone embodiment of the invention.

FIG. 2 is a similar diagrammatic cross-sectional view of anotherembodiment of the invention.

Briefly, in the practice of the invention, advantage is taken of thefact that while the rotor shaft performs an orbital path in a circle,any cross-section of the rotor simply oscillates back and forth along astraight line.

3,203,350 Patented Aug. 31, 1965 This phenomenon was known to Moineaubut its significance in rotor phasing has not heretofore beenappreciated. With any cross-section of the rotor oscillating back andforth along a straight line, it is clear that, assuming the orientationof the rotor to be fixed by virtue of its being in a single piece withanother rotor in engagement with a fixed stator, the second stator mustbe oriented in such a way that this straight line oscillation of therotor can take place. Otherwise the apparatus will bind and the pumpcannot be driven.

In accordance with the present invention, the second stator is not fixedbut is bonded to a sleeve which is rotatable within the pump casing. Asa result of this construction, the second stator is self-aligning orself-orienting during the initial rotation of the rotor and thereafterremains in its oriented position.

Referring now in more detail to the drawings, there is shown in FIG. 1 apump having a casing 10. The casing 10 has an inlet or suction port at11 which communicates by means of ducts 12 and 13 with the intake endsof the two sets of pumping elements as shown. A discharge port 14 isprovided between the two sets of pumping elements and the fluid beingpumped follows the direction of the arrows.

One set of pumping elements is shown at 15 and 16, 15 being the statorand being fixed within the housing 10. In the particular embodimentshown, the stator 15 has two threads while the rotor 16 has a singlethread. The pump drive shaft is indicated at 17 and is provided withsuitable bearings 18 and a suitable seal 19. The drive shaft 17 isconnected to the rotor 16 by means of the double universal jointindicated generally at 20. The joint 20 permits rotation of the rotor 16and also the orbital movement in a circle having a radius e, which isknown as the eccentricity of the rotor.

The rotor 16 is connected by a shaft or the like 21 to the rotor 22 ofthe second pair of helical screw elements which cooperates with a stator23. It will be understood that the two rotors 16 and 22 are fixedtogether to rotate and nutate together. Under these circumstances, theorientation or phasing of the stator 23 is of critical importance.

According to the present invention, the stator 23 is not fixed but isbonded to a metallic sleeve 24 which is free to rotate in the pumphousing 10. The pump housing is provided with a shoulder 25 whichdefines the axial position of the stator 23.

It will now be understood that if the shaft 17 is rotated by means of asuitable source of power (not shown) the two rotors 16 and 22 willrotate and orbit in a circular path. If the stator 15 were not inposition, the rotatable stator 23 would simply rotate with the rotor 22and no pumping action would result. However, with the stator 15 fixed inposition the rotors 16 and 22 are forced to nutate in a directionopposite to the direction of rotation and each cross-section of therotor 22 oscillates back and forth along a straight line. There is,practically speaking, only one position of orientation of the stator 23which permits free movement of all the cross-sections of the rotor 22 ina straight line. (The other such position is theoretical only, since thestator would have to move axially in order to rotate Therefore, as thepump starts, the rotor 22 rotates the stator 23 slightly until the idealposition is reached, whereupon the straight line oscillation referred tocan take place and thereafter the stator 23 remains in its properlyaligned or oriented position. As the pumping pressure builds up there isa thrust in a direction opposite to the pumping direction and thisthrust pushes the stator 23 against the shoulder 25 in the pump housing10. The Wear between the stator 23 and shoulder 25 is negligible becauseas soon as the pump is running and the stator is oriented, there is norelative motion between the stator 23 and the shoulder 25 and the thrustseals off the suction end of the pumping elements constituted by therotor 22 and stator 23.

The embodiment of FIG. 2 operates in exactly the same way as that ofFIG. 1, except that the casing is of a different configuration and therotors 16a and 2211 have a bore therethrough which extends also throughthe connecting portion 21a. Openings are provided at 26 to permitaccess'of the fluid being pumped to the passage 27 through the rotors16a and 22a and the connecting portion 21a. In this embodiment,therefore, fluid being pumped enters the pump at 11 and a portion of thefluid is pumped by the pockets between the elements and 16a and aportion of the fluid is drawn through the openings 26 and the passage 27to the chamber 28 at the entrance end of the pumping elementsconstituted by the stator 23 and rotor 22a. From the chamber 28 thefluid is pumped by the pockets between the members 22a and 23 and joinsthe fluid pumped between the members 15 and 16a in passing out throughthe pump outlet 14. The arrows in the figure indicate the direction offlow.

It will be understood that details as to the connection of the drivingmeans to the rotors can be varied and that the device could be drivenfrom either end or even from the middle as. suggested by Moineau. Inorder to have a proper motion in both sides of the multiple pump, it isonly necessary that the eccentricities of the rotors of the two sectionsbe identical. In order to balance out the thrust on the double universaljoint 20, it is only necessary that the diameters of the two rotors beapproximately the same. The pitch of the two sections of the multiplepump need not be the same because the pitch has to do only with thetheoretical volume of the pump and in some cases it may be desirable tohave one pair of pumping elements pumping a larger volume than theother. The theoretical volume of the pump will be:

wherein e is the eccentricity, D and D are the diameters of the twosections respectively, and P and P are the pitches of the two sectionsrespectively. It will also be understood that it is not necessary thatthe pumping action be from the outer ends of the multiple pump towardthe middle. The pumping could take place in a reverse direction with theportion 14 being the inlet port and the port 11 being the outlet port bysimply reversing the rotation of the shaft 17. If this were done, itwill of course be understood that the shoulder would have to be providedat the other end of the stator 23, as indicated in broken lines at 25a,and eliminated at the outboard end of the stator as shown in brokenlines at 25b.

No limitations not specifically set forth in the claims are intended.

What is claimed is:

It. A multiple pump comprising a casing having an inlet and an outletand comprising two outer helical screw elements in axially spacedrelation, and two inner helical screw elements in engagement therewithrespectively, each of said outer elements having one more threadrespectively than the inner element engaged therewith, the threads ofone engaging set of inner and outer elements being of opposite hand fromthe threads of the other set of inner and outer elements, said innerelements being fixed together coaxially to constitute a common rotor,one of said outer elements being fixed in said casing, and the other ofsaid outer elements being free to rotate in said casing to the extentpermitted by interference with the inne-r element, whereby it isself-aligning as to phase with respect to the inner element engagedtherein and said two sets of inner and outer elements may coactpumpingly without binding.

2. A pump according to claim 1, wherein said casing is provided with aninternal shoulder coacting with the intake end of that outer elementwhichis free to rotate, to fix the position of said last named outerelement axially.

3. A pump according to claim 1, wherein the direction of rotation ofsaid common rotor is such as to produce a pumping action by said twosets of inner and outer elements toward each other, and wherein saidoutlet is located between said sets.

4. A pump according to claim 3, wherein said casing is provided with aninternal shoulder coacting with the outer end of that outer elementwhich is free to rotate, to fix the position of said last named outerelement axially.

5. A pump according to claim 4, wherein said casing is provided withinternal ducts leading from said inlet to the intake ends of the twosets of inner and outer elements.

6. A pump according to claim 4, wherein said inlet is located near oneend of said pump, adjacent the intake end of one set of inner and outerelements, said common rotor having an axial passage therethrough and incommunication with said inlet, and providing a duct to the intake end ofthe other set of pumping elements.

References Cited by the Examiner UNITED STATES PATENTS 2,329,386 9/43Brennan 1031 17 2,483,370 9/49 Moineau 103-4 2,525,265 10/50 Moineau103117 FOREIGN PATENTS 436,843 10/35 Great Britain.

LAURENCE v. EFNER, Primary Examiner.

1. A MULTIPLE PUMP COMPRISING A CASING HAVING AN INLET AND AN OUTLET ANDCOMPRISING TWO OUTER HELICAL SCREW ELEMENTS IN AXIALLY SPACED RELATION,AND TWO INNER HELICAL SCREW ELEMENTS IN ENGAGEMENT THEREWITHRESPECTIVELY, EACH OF SAID OUTER ELEMENTS HAVING OINE MORE THREADRESPECTIVELY THAN THE INNER ELEMENT ENGAGED THEREWITH, THE THREADS OFONE ENGAGING SET OF INNER AND OUTER ELEMENTS BEING OF OPPOSITE HAND FROMTHE THREADS OF THE OTHER SET OF INNER AND OUTER ELEMENT, SAID INNERELEMENTS BEING FIXED TOGETHER COAXIALLY TO CONSTITUTE A COMMON ROTOR,ONE OF SAID OUTER ELEMENTS BEING FIXED IN SAID CASING, AND THE OTHER OFSAID OUTER ELEMENTS BEING FREE TO ROTATE IN SIAD CASING TO THE EXTENTPERMITTED BY INTERFERENCE WITHH THE INNER ELEMENT, WHEREBY IT ISSELF-ALIGNING AS TO PHASE WITH RESPECT TO THE INNER ELEMENT ENGAGEDTHEREIN AND SAID TWO SETS OF INNER AND OUTER ELEMENTS MAY COACT PUMPINGLWITHOUT BINDING.